The present invention relates to the field of seismic exploration. More particularly, the invention relates to a deck configuration for an ocean bottom seismometer launch platform and most particularly, the invention relates to a deck configuration that enhances the handling and manipulation of the multiplicity of ocean bottom seismometers that are typically deployed and retrieved in deep marine seismic exploration operations.
Seismic exploration operations in marine environments typically are conducted from the deck of one or more seismic exploration vessels, such as floating platforms or ships. While the fundamental process for detection and recording of seismic reflections is the same on land and in marine environments, marine environments present unique problems due to the body of water overlaying the earth's surface, not the least of which is moving personnel and equipment to a site and maintaining them there for an extended period of time. In this same vein, even simple deployment and retrieval of seismic receiver units in marine environments can be complicated since operations must be conducted from the deck of a seismic exploration vessel where external elements such as wave action, weather and limited space can greatly effect the operation.
These factors have become even more significant as exploration operations have moved to deeper and deeper water in recent years, where operations require longer periods of time “at sea.” Among other things, exploration in deep water has resulted in an increased reliance on seismic receiver units that are placed on or near the seabed. These devices are typically referred to as “OBC” (Ocean Bottom Cabling) or “OBS” (Ocean Bottom Seismometer) systems. Most desirable among these ocean bottom systems are OBS system known as Seafloor Seismic Recorders (SSR's). These devices contain seismic sensors and electronics in sealed packages, and record seismic data on-board the units while deployed on the seafloor (as opposed to digitizing and transmitting the data to an external recorder). Data are retrieved by retrieving the units from the seafloor. SSRs are typically re-usable.
In a typical operation, hundreds if not thousands of OBS units are deployed in a seismic survey. For SSRs, these units must be tracked, charged, deployed, retrieved, serviced, tested, stored and re-deployed all from the very limited confines of the deck of the surface vessel. Because of the large number of OBS units that must be handled, additional surface vessels may be employed. Additional surface vessels are costly, as are the personnel necessary to man such vessels. The presence of additional personnel and vessels also increases the likelihood of accident or injury, especially in deep water, open-sea environments where weather can quickly deteriorate.
One particular problem that arises in offshore seismic operations is the manipulation and movement of these OBS units on a vessel's launch/recovery deck when weather and ocean conditions are onerous. Typically an overhead crane on a vessel's deck is utilized to grasp and move equipment from one location to another, such as moving OBS units from a storage area to a launch area. These cranes are generally tower cranes that must lift a load relatively high above the deck in order to clear other equipment and structures on the deck. However, those skilled in the art understand that as such equipment is lifted clear of the deck, it will have a tendency to swing on the gantry's lifting line, which can create a safety hazard. This is especially problematic for a vessel operating in rough seas or windy conditions. In such cases, operations may have to be suspended until they can be conducted without endangering personnel, equipment or both.
Nowhere in the prior art is there described a launch/recovery deck system for handling the above-described OBS units, ancillary equipment and operations, whether it be storage of the units or deploying and retrieving the units or any other equipment associated therewith, such as Remote Operated Vehicles (“ROVs”) that might be used in the operations. As the size of deep water seismic recorder arrays becomes larger, a system for efficiently and safely storing, tracking, servicing and handling the thousands of recorder units comprising such an array becomes more necessary.
Thus, it would be desirable to provided a system on the deck of an OBS deployment/retrieval vessel for efficiently handling the hundreds or thousands of OBS units that can comprise an array. Such a system should permit the safe handling and efficient movement of OBS units and their storage containers along the deck, even under adverse weather or ocean conditions. Such a system should facilitate the deployment, retrieval, tracking, maintenance and storage of OBS units, while minimizing manpower and the need for additional surface vessels. The system should likewise minimize potential damage to the individual units during such activity.